21008763137 has 12 divisors (see below), whose sum is σ = 21603008460. Its totient is φ = 20430359040.

The previous prime is 21008763119. The next prime is 21008763173. The reversal of 21008763137 is 73136780012.

It is a Cunningham number, because it is equal to 144944²+1.

It can be written as a sum of positive squares in 6 ways, for example, as 15775108801 + 5233654336 = 125599^2 + 72344^2 .

It is not a de Polignac number, because 21008763137 - 2¹² = 21008759041 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21008763137.

It is not an unprimeable number, because it can be changed into a prime (21008763107) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 506189 + ... + 546117.

It is an arithmetic number, because the mean of its divisors is an integer number (1800250705).

Almost surely, 2^21008763137 is an apocalyptic number.

It is an amenable number.

21008763137 is a deficient number, since it is larger than the sum of its proper divisors (594245323).

21008763137 is an equidigital number, since it uses as much as digits as its factorization.

21008763137 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40324 (or 40283 counting only the distinct ones).

The product of its (nonzero) digits is 42336, while the sum is 38.

The spelling of 21008763137 in words is "twenty-one billion, eight million, seven hundred sixty-three thousand, one hundred thirty-seven".